Obstructive sleep apnea is a major source of cardiovascular morbidity and mortality for which conventional treatment is poorly tolerated and effective pharmacotherapy is lacking. Efforts to develop pharmacotherapy have been hindered by a lack of fundamental insight and translational models of this disorder. We will address this gap by dissecting underlying pathogenic mechanisms of upper airway obstruction in obesity during sleep with the overall objective of piloting novel therapy in specific murine strains. Our proposal is predicated on novel findings that obese leptin deficient and leptin resistant mice have obstructive sleep apnea and that leptin abolishes sleep apnea in leptin deficiency, independent of changes in body weight. Our central hypothesis is that strategies to replete leptin and overcome leptin resistance will treat obstructive sleep apnea through actions at specific CNS sites. To address this hypothesis, we will examine obese mice with specific leptin defects: 1) ob/ob mice with leptin deficiency; 2) db/db mice with leptin ObRb receptor deficiency; 3) New Zealand obese (NZO) mice with reduced leptin permeability to the CNS at the blood brain barrier (BBB); 4) C57BL/6J diet-induced obese (DIO) mice with reduced BBB permeability and impaired leptin receptor signaling. State of the art techniques will be deployed to treat lepti signaling defects in these mouse models, including intracerebroventricular (ICV) and intranasal leptin administration, and gene transfer. Sites of leptin's effects on the upper airway will be identified by co- staining for leptin signaling and transneuronal tracer Pseudorabies virus (PRV) and then localized to specific brain nuclei by insertion of the ObRb receptor using an adenovirus. In SA1, we will examine effects of leptin replacement on sleep apnea in ob/ob mice. We hypothesize that leptin deficiency causes obstructive sleep apnea, which can be (a) reversed by acute administration of leptin ICV to the lateral and fourth ventricles, and can be (b) treated by subcutaneous leptin administration. In SA2, we will localize and reverse leptin signaling defects in specific brain nuclei and treat obstructive sleep apnea in leptin-resistant db/db mice. We hypothesize that db/db mice lacking the ObRb leptin receptor will have obstructive sleep apnea that will be treated by insertion of functional ObRb receptors in specific brain nuclei. In SA3 and 4, we will treat sleep apnea in NZO and DIO mice by overcoming leptin resistance. We hypothesize that reduced BBB permeability for leptin causes sleep apnea in NZO mice, and, therefore it will be reversed by ICV and intranasal leptin. In DIO mice, sleep apnea is caused by both the BBB and ObRb receptor signaling defects and a combination of intranasal leptin and low fat diet will be required to treat apnea. Our translational proposal will lay the groundwork for developing novel pharmacotherapy for sleep apnea by targeting leptin signaling.